This invention relates to a molding device for concrete construction which can be released easily from a formed concrete structure and easily reset at another location for a next molding.
It is known in the art to provide molding devices which can be collapsed or contracted to be released from a formed concrete structure and which can be stretched to a molding position. Various types of collapsible molding devices have been suggested in the art. For example, U.S. Pat. Nos. 2,544,297, 3,614,054, 3,934,808 and French Pat. No. 2489206 disclose inner formwork boards used to form inner sides of multi-sided concrete walls. These formwork boards incorporate hydraulically operated linkage mechanisms which hold and operate the formwork boards. U.S. Pat. No. 4,679,762 of the inventor of this application discloses a form assembly which is used to form an enclosed multi-sided wall as shown in FIG. 1 and includes component boards and wedge-shaped spacer boards which are operated by a rack-and-gear mechanism including a plurality of worm wheels mounted on vertical shafts and horizontal shafts to drive rack members. To release this form assembly, the spacer boards must be moved inward simultaneously. When the spacer boards are moved, the form boards on two sides of the spacer boards also move simultaneously so that a great deal of force is needed to simultaneously release the entire form assembly. Accordingly, a powerful hydraulic device is necessary for operation. Moreover, this form assembly is suitable only for forming enclosed multi-sided walls.